Convert the Boolean (or 1/0) field to "R" for True / 1 and "Q" for False / 0
You can do this either in SQL or using an IIF expression
SQL
,CASE
WHEN BooleanField = 1
THEN 'R'
ELSE 'Q'
END AS BooleanField
IIF Expression
=IIF(Fields!BooleanField.Value = True, "R", "Q")
The original field doesn't necessarily have to be Boolean e.g. Does final score pass exam:
=IIF(Fields!FinalScore.Value >= 50, "R", "Q")
Now just format the textbox to Wingdings2

And this is what you get:
